mongoose/examples/load_balancer

Mongoose-based HTTP load balancer

Configuration

Load balancer is configured with command-line flags.

Global flags

• -p port – TCP port to listen on. Default: 8000.
• -l log_file – path to the log file. Default: none.
• -s ssl_cert – path to SSL certificate. Default: none.

Backend configuration

Main flag is -b uri_prefix host_port – it adds a new backend for a given URI prefix. Example: -b /stuff/ 127.0.0.1:8080 will route all requests that start with '/stuff/' to a backend at port 8080 on localhost. There is a special syntax for uri_prefix that allows you to change the URIs that get passed to backends:

• -b /stuff/=/ 127.0.0.1:8080 – for '/stuff/thing' backend will see '/thing'.
• -b /stuff/=/other/ 127.0.0.1:8080 – '/stuff/thing' => '/other/thing'.

Also there are few per-backend flags that can be placed before -b and apply only to the next backend:

• -r – instead of proxying requests load balancer will reply with 302 redirect.
• -v vhost – match not only URI prefix but 'Host:' header as well.

Example

load_balancer -s path/to/cert.pem \
  -v example.com -b /site/=/ 127.0.0.1:8080 \
  -b /static/ 127.0.0.1:8081 \
  -b /static/ 127.0.0.1:8082

In this example requests to 'example.com/site/' will be forwarded to the backend on port 8080 with '/site' prefix stripped off and requests to '/static/' on any virtual host will be balanced in round-robin fashion between backends on ports 8081 and 8082.